A supercapacitor with ultrahigh volumetric capacitance produced by self-assembly of reduced graphene oxide through phosphoric acid treatment

Reduced graphene oxide (RGO) with a porous nanostructure and large surface area suffers from poor volumetric capacitance when it is employed in supercapacitors. This paper reports a facile, scalable and efficient method to produce self-assembled reduced graphene oxide with high packing density (1.55 g cm(-3))viaphosphoric acid treatment (PAT) at moderate temperatures (200-400 degrees C). The PAT process could not only controllably preserve redox-active C-OH and CO groups which can provide large and stable pseudocapacitance, but also contribute to the formation of a well self-assembled compact structure. Due to the pseudocapacitive behavior of the electrochemically active oxygen functional groups as well as the compact layered structure, the reduced graphene oxide (RGO-MP40) exhibits an ultrahigh volumetric capacitance (482 F cm(-3)and 384 F cm(-3)at a mass loading of 2.5 mg cm(-2)and 19.7 mg cm(-2), respectively). This novel strategy holds great promise for designing graphene-based materials for compact energy-storage devices.